1. Field of the Invention
The present invention relates to a content management apparatus, a content management system, and a content management program, for managing contents provided via a network.
2. Related Background Art
Recently, there have been many cases to connect electronic equipments such as audio devices, video devices, personal computers, and information equipments via a network, in order to transfer information between them. In these cases, it is necessary to prescribe operation method of the equipments and procedure for associating with each other as standards, and to operate the equipments in according with the standards. One of such standards is UPnP AV (Universal Plug and Play/Audio and Visual), the UPnP is a specification for the AV (see US Patent Application Publication No. 2002-0035621 A1).
The UPnP AV adopts a model in which a media server and a media renderer, being two types of devices, are controlled by a control point, being a device of a separate type. The media server plays a role of storing contents and as a source for streaming. The media renderer plays a role of reproducing the contents and as a sink for streaming. The control point inquires of the media server about a location of a content, selects a media renderer agreeing with the source capability for streaming, and establishes a stream transmission line between these two devices (the media server and the media renderer) to control the transmission (see Japanese Patent Application Laid-open No. 2002-304333).
In the UPnP AV media server, a content directory service (CDS) performs a role of storing contents and responding to inquiries of content information from the control point. The CDS stores metadata of contents, so that the control point can perform functions of browsing the content hierarchy, searching the attribute, creating and deleting the content, and changing the attribute.
The metadata includes the title, the artist, and the format of the contents, and the location of the media resource (hereinafter, “res value”), and these are described in the Extensible Markup Language (XML). The control point sets the res value of the metadata obtained by the inquiry to the CDS, in the media source of the media server or the media sink of the media renderer, as a location of the media resource to be referred to, and sets a transmission path between the media source of the media server and the media sink of the media renderer. The res value is given by the Uniform Resource Identifier (URI) RFC2396 (see internet Engineering Task Force (IETF) web site).
The description format of the URI is given by <scheme>://<scheme-specific-part>, or <scheme>://<authority><path>?<query>. For example, it is provided such as http://192.168.10.111:8080/MyMusic.sample.mp3.
In this case, “http” denotes the scheme, “192.168.10.111:8080” denotes the authority, and “/MyMusic/sample.mp3” denotes the path, indicating that it is a media resource referred to as “/MyMusic/sample.mp3” accessible through a port number. 8080 of the host 192.168.10.111, by using the HyperText Transfer Protocol (HTTP) protocol.
In many cases, the authority part is expressed by a set of a host name and a port number, and the host name is Domain Name Service (DNS), and a Fully Quantified Domain Name (FQDN) capable of performing name resolution to an IP address or the IP address itself is used therefor.
One of the functions of the media server is storage of the contents, and the media resource may be outside of the media server. In this case, the media resource exists in the equipment around the media server or in a media distribution site on the Wide Area Network (WAN) or the Internet, and the content corresponding to the equipment is set in the authority part of the res value.
There is a problem for a handling in the case where the IP address itself is set in the authority part. When any of the name resolution means such as assignment by FQDN is provided, there is no problem since the host name can be converted to an IP address by the name resolution means.
When the IP address itself is set, it is necessary to determine whether the IP address is static or dynamic. That is, the IP address in the authority part of the res value of the media resource stored in the equipment to which a dynamic address is allocated should change with a lapse of time, but there is no way to know that. In this case, the res value returned from the CDS becomes an unintended value different from the former value.
However, there is a problem in that the workload is very large for reconstruction at the time of startup operation of the CDS. This becomes noticeable in the in-house use or the like in which the respective equipment operate autonomously, including the allocation of the IP address.
Therefore, it is desired to provide the CDS which changes following a change in the IP address of the equipment, in terms of the media resource held by the equipment in which the IP address can change dynamically.